1. Electrical Terminology & Theory
Ag Mech I
Standard 7:1-7

2. Terminology
Electricity-form of energy that can produce light, heat, magnetism and chemical changes
Filament-special metal element that can produce light by heating it in a vacuum tube called a bulb
Fluorescent light- glows as a result of electricity flowing through a gas
Resistance-any tendency of a material to prevent electrical flow
Conductor-metal that allows electricity to flow easily (silver, copper then alumnium
Insulator-material that provides great resistance to the flow of electricity
Amperes- measure of the rate of flow of electricity
Volts-measure of electrical pressure

3. Terminology
Watts-measure of the amount of energy or work that can be done by amps and volts
Ohm-unit used to measure a materials resistance to the flow of electrical current
Ohm’s law- the relationship between electric current, electromotive force and resistance formula is E=IR Volts(E), Amps(I) and resistance(R)
Volt-ohm-millampere meter-popular meter that measures volts, ohms, and amps
Milliampere-one thousandth of an amp
Magnetism-force that attracts or repels iron or steel
Permanent Magnet-if iron or steel holds its magnetism

4. Terminology Poles-the 2 ends of a magnet
North pole-the end of a magnet that attracts the south pole of a magnet but repels the north pole
Attraction-part of a magnet that pulls metal in its direction
Repulsion-part of a magnet that repels metal
South pole- pole-the end of a magnet that repels the south pole of a magnet but attracts the north pole
Magnetic flux-lines of magnetic force that occur in the air between 2 poles
Magnetic field-the pattern of a magnetic flux

5. Terminology
Reversing the polarity-reversing the direction of current flow
Electromagnet-a core of magnetic material surrounded by a coil of wire through which an electric current is passed to magnetize the core
Commutator-a part on an electric motor that reverses the current
Armature-the rotating magnet in an electric motor
Field-magnetic forces around an armature
Generator-produces direct current electricity which flows in 1 direction
Alternator-produces electricity which reverses in direction each time the armature turns

6. Terminology
Turbine-high speed rotary engine driven by water steam or other gasses
Circuit-2 or more wires connected to a load such as a light heater or motor are known collectively as a circuit
Open circuit- likened to a circle if the circle is broken it is said to be open
Short circuit-a condition that occurs when electricity flows back to its source too rapidly and blows fuses burns wires and drains batteries
Grounding-making an additional connection between a piece of equipment and earth
Rod- pipe driven in the ground and connected to the service panel to provide a ground
Wire-used to connect electrical devices and the electrical source

7. Terminology Shock-the bodies reaction to electrical current
Ground-fault-circuit interrupter (GFIC)-a device that cuts off the electricity even if tiny amounts of current leaves the circuit
Entrance head-is a waterproof device used to attach exterior wires to interior wires of a building
Transformer-converts high voltage from the power lines to 240volts for home and farm use
Service drop-assembly of wires that connects the transformer to the entrance head
Service entrance panel-is the box with fuses or circuit breakers where electricity enters the building
Meter-used to measure the amount of electricity that passes through it

8. Terminology Kilometer-1000 meters
Watt-hour-the use of 1 watt for 1 hour (a 100 watt light bulb used for 1 hour will consume 100 watt hours of electricity)
Kilowatt-hour-is the use of 1000 watts in 1 hour
Branch circuits-circuits that begin from the service entrance panel
Fuse-a plug or cartridge containing a strip of metal that melts when more than the specified amount of current passes through it
Circuit breaker-a switch that trips or breaks when more than the specified amount of current passes through it
Nonmetallic sheathed cable-copper or Al wires covered with paper or vinyl for insulation or protection
Armored cable-flexible metal sheath with individual wires inside

9. Terminology Conduit-tubing that contains individual insulated wires
Electrical metallic tubing (EMT)- bendable type of metal conduit
Strands-small wires placed together to form bundles for wire No.8 and larger to improve flexibility and conductivity
Voltage drop-refers to the loss of voltage as in travels along a wire
Positive (hot) wires-carry electrical current to devices
Neutral wires- carry current back to the source
New work-when wiring up a new house or business, normally through wall and floors

10. Terminology
Fixture-a base or housing for lightbulbs, fan motors and other electrical devices
Wire nuts-insulated solderless wire connectors
Receptacle-a device for receiving an electrical plug
Switch-a device used to stop the flow of electricity
Duplex receptacle-is wired so that both outlets are on the same circuit
Splitting the receptacle-remove the metal strip connecting the screws and wiring to different circuits

11. Terminology
Single pole switch-is a switch designed to be the only switch in a circuit
Knockout-a partially punched impression that can be punched out and removed so a cable can pass through to the service panel
Ground clip (gee)-attached the ground wire to the metal box
Continuity tester-a device used to determine if electricity can flow between 2 points
Continuity- connectedness
Three-way switch-a switch that when used in a pair permits a light or receptacle to be controlled from 2 different locations
Common terminal(traveler)-where current flows in a 3 way switch it is the dark screw
Switching wires-where the other 2 wires connect in a 3 way switch
Four-way switch-a switch connected in the pair traveler wires between 2 three-way switches

12. Principles of Electricity
Electricity comes in many forms and can produce light, heat, magnetism and chemical changes
Light is produced by heating up a filament in a bulb, the flow of electricity must be carefully controlled so the filament glows without burning out.
Electricity flowing through certain gases causing them to glow this is a fluorescent light
These tubes contain mercury and usually an inert gas argon
Heat is produced when electricity passes through metals with some difficulty

13. Principles of Electricity
Any tendency of a material to prevent electrical flow is called resistance
If electricity flows easily is called a good conductor
Silver is the best followed by copper then aluminum
Silver is very expensive and is rarely used
Copper is used inside buildings
Aluminum is used outside where heat buildup is not a problem
Aluminum is no longer used in branch circuits smaller the 8 gauge

14. Principles of Electricity
Heat in wires, switches, outlets, motors and lights is not desirable
It waste electricity, causes materials to deteriorate and heats up surrounding areas and may cause fires
Proper design of electrical systems is very important
In heating systems where heat is desired the heat is produced by elements with just the right amount of resistance

15. Principles of Electricity
A material that provides great resistance to the flow of electricity is called an insulator
Examples of good insulators are
Rubber
Glass
Vinyl
Air
Anyone working with electricity must be aware the insulators are relative to what you are working with
A thin pair of rubber gloves may work when dealing with the 12volts on your car but will provide no safety if working with 30,000 volts a spark plug wire produces

16. Amperes, Volts & Watts
We must understand Amps, Volts and watts to design electrical circuits or install electrical materials safely
Amps measure the rate of flow of electricity in a conductor
Volts measures electrical pressure
Watts measure the amount of energy or work that can be done by amps and volts
This is the equation Watts= Volts X Amps

17. Amperes, Volts & Watts
Example if a 200 watt lightbulb operates at 120 volts it will draw 1.67 amps of electricity 200/120 = 1.67
A 5 amp motor running on 12o volts will consume 600 watts of electricity W= V x A or 120 x 5 = 600
A refrigerator rated a 3 amps that consumes 360 watts of electricity should be plugged into a 120 volt circuit
V= W/A 360/3=120 volts
This is the West Virgina formula W=VA

18. Ohm’s LAW Named after physicist George Simon Ohm
Made several discoveries about electrical current
As a result the unit used to measure a materials resistance to the flow of electrical current is know as Ohm’s law
He discovered that the flow of electricity through a conductor is directly proportional to the electrical or electromotive force that produces it
The relationship he discovered between electric current, electromotive force and resistance is called Ohm’s Law

19. Ohm’s LAW
Electromotive force is measured in volts and is represented by a capital E
The rate of flow in electricity through a conductor is measured in amps and is represented by a capital I
The tendency of a material to prevent electrical flow or resistance is represented by a capital R
E=IR
All can be measured by various meters

20. Magnetism and Electricity
Electricity flowing through a conductor results in magnetism
Magnetism can also be created by exposing iron or steel to magnetic forces
Magnets have 2 poles a north and south the repel and attract metal
Lines of magnetic force are called magnetic flux
The pattern is referred to as the magnetic field

21. Electric Motors
The principle of magnetism is the basic upon which electric motors operate
A strong magnet can be made by wrapping many coils of insulated wire around an iron core and passing electric current through it

22. Electric Motors
If the wires are switched to opposite battery terminals the poles of the magnet will reverse, but the magnetic field will remain
Reversing the direction of the current flow reverses the polarity of the magnet
This is called an electromagnet

23. Electric Motors
A motor may be made by bending the electromagnet into the shape of a horseshoe and suspending a permanent magnet on a bearing between the poles
When current flows the unlike poles of the electromagnet and the permanent magnet will attract each other, causing the permeant magnet to make ½ turns

24. Electric Motors
If the wires are reversed at the battery the direction of the current and polarity of the magnet will be reversed and the permanent will make another ½ turn
In a motor the current is reversed by a part called the commutator
The commutator causes the motor to run continuously in the same direction, the rotating magnet is called the armature and the magnetic forces around the armature are called the field

25. Electric Motors
Devices that produce electricity by magnetism are called generators and alternators
A generator provides direct current which means electricity flows in 1 direction
An alternator produces alternating current which reverses in direction or alternates each time the armature turns
Generators & Alternators must be powered by human, animal power, water wheel, gas or diesel engine, turbine or an electric motor getting electricity from a separate source
A turbine is q high speed rotary engine driven by water, steam or other gases

26. Electric Motors
Electric Motor Maintenance-Modern electric motors are designed for long life with little maintenance
Many have permanently lubricated bearings
Older motors have 2 oil cups or tubes with a wick to hold oil for the 2 shaft bearings
Most manuals call for 10 drops per year
More causes dirt to build up
Less oil causes bearing wear and eventual bearing failure

27. Circuits
A source of electricity plus 2 or more wires connected to a load such as a light, heater, or motor are known collectively as a circuit.
A circuit may be likened to a circle
If the circle is broken so that current cannot flow through it, it is aid to be an open circuit
All circuits must include an object with resistance that falls within a certain range
Otherwise the electricity will flow through the circuit and back to its source too rapidly and blow fuses, burn wires and drain batteries. This condition is known as a short circuit

28. Circuits
Electricity can travel back to its source through earth as well as through a wire
A circuit always includes a wire to carry the current back to its source
Safety requires that an additional wire or conductor be provided to all metal parts in the system in case the current gets out of its circuit
Making this additional connection between a piece of equipment and the earth is called grounding
We do this by driving a steel rod at least 1 inch in diameter into the ground that is always moist and connect it with a wire to the service panel

29. Circuits Grounding equipment is a standard safety practice
In this way electricity that accidentally gets out of its circuit its channeled to the earth through a ground wire rather than through the body of a human or animal
In extreme dry weather a grounding rod may not work

30. ELECTRICAL SAFETY
There are 2 deadly hazards associated with electric current SHOCK & FIRE
Shock refers to the body’s reaction to an electrical current
Shock can interfere with a normal heart beat and result in the injury and death of the victim
Fire may result when electrical conductors overheat or when a spark is produced by an electrical current jumping an air space and igniting flammable material nearby

31. ELECTRICAL SAFETY Safety Protocols
Never disconnect or damage any safety device
Do not touch electrical appliances, boxes or wiring with wet hands or feet
Do not remove the long ground prong from a 3 prong 120 volt plug
Use GFCI plugs in kitchen, bathroom, laundry and outdoor circuits or wherever moisture may be present

32. ELECTRICAL SAFETY
A ground fault circuit interrupter (GFCI) is a device that cuts off the electricity even if tiny amounts of current leave the normal circuit
This device reduces the like hood of human shock injury

33. ELECTRICAL SAFETY
Immediately discontinue the use of any extension cord that feels warm or smells like burning rubber
Do not place extension cords under carpeting
Install all electrical wiring according to the specifications of the National Electrical Code
Use only double insulated portable tools or tools with 3 wire grounded cords
If a fuse is blown or circuit breaker is tripped determine the correct problem before inserting a new fuse or resetting the breaker

34. ELECTRICAL SAFETY
Do not install larger fuse or circuit breaker, fire danger
Do not remove the back of a TV it has 20,000-30,000 volts
Keep electrical motors lubricated and free of dirt

35. Electrical Wiring
An electrical system must meet several conditions to be satisfactory
-be safe
-be convenient
-be expandable
-look neat
-provide sufficient current

36. Electrical Wiring Service Entrance
Electricity comes into a building by overhead or underground wires
The power company provides a transformer, service drop, and appropriate wiring to an entrance head
The entrance head is a waterproof device used to attached exterior wires to interior wires
Most new homes use underground wires that eliminates the entrance head

37. Electrical Wiring Transformer
The transforms converts high voltage from power lines to 240 volts for home and farm installations
The service drop is an assembly of wires, connectors and fasteners used to transmit electricity from the transformer to the service panel
Service entrance panel is a box of fuses or circuit breakers were electricity enters a building
transformer-service drop-entrance head-electric meter-service entrance panel

38. Electrical Wiring

39. Branch Circuits Begin at the service entrance panel
Branch circuits then run to various parts of the house or barn
Branch circuit usually contains only 1 motor or a series of outlets or a series of light fixtures
It is important to provide the correct size wire and fuse or circuit breaker for the load on each circuit

40. Branch Circuits
Fuse is a plug or cartridge containing a strip of metal that melts when more than the allowed current passes through it

41. Branch Circuits
Circuit breaker is a switch that trips and breaks the circuit when more than the specified amount of current passes through it
Circuit breakers can be reset after tripping

42. Types of cable 3 types of cable Nonmetallic sheathed cable
Copper or aluminum wire covered with paper and vinyl
Water proof and suitable for underground burial

43. Types of cable Armored cable
Consists of flexible metal sheath with individual wires inside
The wires are wrapped in vinyl and paper for protection
Protects from mechanical damage
Don’t use in wet areas

44. Conduit Tubing that contains individual insulated wires
Tubing sizes ½”-3/4”, 1” or larger sizes
Plastic or metal
Bendable metal conduit called EMT-electrical metallic tubing

45. Residential Service Entrance Panel

46. Standard electrical symbols
Figure page 513

47. Wire type and size
Individual wires within cabling or conduit may be aluminum or copper
Wire size is designated by gauge or AWG (American Wire Gauge) number
The lower the gauge number the larger in diameter the wire is
14 AWG copper is used for 15 amp circuits 120 volts
12 AWG copper used for 20 amp 120 volts
10 AWG copper used for 30 amp 120 volts
If using aluminum wire it is necessary to go up one wire size when compared to copper
Do not connect copper to aluminum without a special connector they corrode when connected

48. Electrical wire size chart

49. Wire type and size
For No. 8 AWG and larger wires called strands are put together to improve flexibility and conductivity
Electrical current is carried on the outer surfaces of wire
Stranded wire has more total surface area than solid wire

50. Voltage Drop
Voltage drop refers to the loss of voltage as it travels along a wire
This is caused by electrical resistance in the wire
The longer the cable runs the more resistance the less voltage at the end

51. Voltage Drop
Copy pages

52. Wire identification
The type of outer covering, individual wire covering, cable construction and number of wires all help determine where a cable can be used
The wire type is stamped on the outer surface of the wire or cable or cable covering

53. Wire identification Type T-dry locations only
Type TW- dry or wet locations
Type THHN- dry location high temperature
Type THW and THWN- wet locations high temperature
Type XHHW- high moisture and heat resistance
Type UF- direct burial in soil but not concrete

54. Wire colors Black, Red & Blue- positive hot wires
White – neutral carries power back to source
Green or bare wires are used to ground all metal boxes and appliances
Nonmetallic sheathed cable is generally stamped with a mark that identifies its type, wire size and number of conductors

55. Wire markings 12-2 two strands of No. 12 wire one black and one white
12-2 w/g- two strands of No. 12 wire plus a ground (w/g means with ground) black, white and one green or bare
12-3 three strands of No. 12 wire one black one white and one red or blue
12-3 w/g same as 12-3 with the addition of a green or bare wire for grounding